This application relates generally to cellular telephones.
Cellular telephone networks may be packet-based where information is divided into packets and transmitted in a packet-switched system. Alternatively, cellular telephone networks may be circuit-based or not packet-based.
In packet-based wireless networks, the user is generally charged based on the number of packets that are transmitted. Commonly in circuit-based wireless networks, the user is charged based on connection time.
Generally, cellular telephones are either packet-based or circuit-based, but not both. Some of the reasons for this are that packet-based systems utilize mobility management state information while circuit-based systems do not. Application programs in a given cellular telephone may be unable to discern when to apply packet-based protocols and when to apply circuit-based protocols. In addition, because charges are assessed based on packets in a packet-based network and time in a circuit-based network, it is difficult for conventional cellular telephones to determine how and when to accrue charges.
The 3GPP specification calls for a class A mode that supports both second generation (2G) and third generation (3G) services simultaneously. 3rd Generation Partnership Project; General Packet Radio Service, Service description, Stage 1, (3GTS 22.060 Release 1999). However, the specification does not explain how to smoothly transition between 2G and 3G services.
For example, in third generation (2.5G or 3G) cellular telephone networks, three different mobility management states known as idle, standby and ready are available. A cellular telephone in the ready state is paged periodically to determine whether or not the cellular telephone is available and ready to receive phone calls. After the expiration of a time period without receiving a call (or under other circumstances), the telephone may be transitioned from the ready to the standby state. From the standby state, upon the expiry of a period of time without receiving any calls, the telephone may be transitioned to the idle state.
In the ready state, the phone is ready to receive calls. It is periodically paged in accordance with appropriate page messaging protocol. The standby state involves less paging. Generally, the cellular telephone is in a larger area with a plurality of cells and is paged less often than in the ready state. The least paging is done in the idle state.
Thus, an application running on a cellular telephone that operates both in third generation (2.5G or 3G) and second generation (2G) systems, must be able to handle the different circumstances that arise because of the mobility management states when (and only when) the system is in a third generation or packet-switched environment. The rest of the time the extra constraints raised by mobility management states may be ignored.
Thus, there is a need for a way to transition between circuit-based and packet-based systems in the same cellular telephone without user interaction.